A valve of this type has become known from FR 25 73 658. The pressure in an expiration line of a respirator is maintained at a predetermined value in this known valve by means of a diaphragm valve actuated by a moving coil drive. The actual value of the pressure in the expiration line is measured for this purpose at the gas inlet of the valve and is compared with a preset value. Depending on the deviation of the actual value from the preset value, the diaphragm is lifted off from the valve seat more or less by the moving coil drive.
The drawback of this valve is the limited dynamic range and the tendency to vibrate with a pronounced resonance point. This makes it difficult to use the valve for forms of respiration in which great fluctuations may occur in the expiration pressure, e.g., in the case of assisted spontaneous respiration.